Draw scalable rectangles on document

[Zygmunt]

Hey,

I'm working on Telerik UI for Winforms version 2019 R3. I have to implement in my project below functionality:

1. Pdf file is loaded using RadPdfViewer
2. User can mark using rectangles places on each page of the document
3. After mark place by user I have to get coordinates of the rectangle in current page
4. Each mark should be visible only on the page on witch is drawn
5. Rectangles should be scalable and after scroll should point the same place

Is any possible  to realize above points?

I found something about custom layer https://www.telerik.com/forums/text-selection-and-highlight but the solution is in WPF.

Thanks

[Dess | Tech Support Engineer, Principal]

Hello, Zygmunt,    

RadPdfViewer in the Telerik UI for WinForms suite is purposed to display pdf files. It is not intended to offer drawing functionality over the pdf content. However, RadPdfViewer exposes two events indicating when a page starts and completes a rendering operation. You have access to the Graphics object in the event handler, so you can perform any rendering you need. Additional information is available in the following help article: https://docs.telerik.com/devtools/winforms/controls/pdfviewer/how-to/handle-rendering-events 

As an exception, I have prepared a basic example demonstrating a sample approach how you can draw a rectangle once the document is loaded. The attached gif file illustrates the achieved result. It is just a sample approach and it may not cover all possible cases. 

        public RadForm1()
        {
            InitializeComponent();

            this.radPdfViewer1.LoadDocument(@"..\..\Book1.pdf");
            this.radPdfViewer1.ViewerMode = FixedDocumentViewerMode.None;
            this.radPdfViewer1.PageElementCreating += radPdfViewer1_PageElementCreating; 
        }

        List<Rectangle> rectangles = new List<Rectangle>();

        private void radPdfViewer1_PageElementCreating(object sender, RadFixedPageElementEventArgs e)
        {
            e.PageElement.ElementPainted += PageElement_ElementPainted;  
            e.PageElement.MouseMove += PageElement_MouseMove;
            e.PageElement.MouseUp += PageElement_MouseUp;
        }

        private void PageElement_MouseUp(object sender, MouseEventArgs e)
        {
            RadFixedPageElement page = (sender as RadFixedPageElement);
            Rectangle pageRect = page.ControlBoundingRectangle;
            Rectangle rectInitial = new Rectangle(downLocation, new Size(Math.Abs(location.X - downLocation.X), Math.Abs(location.Y - downLocation.Y)));
            RectangleF rect = new RectangleF(new PointF(-pageRect.X + rectInitial.Location.X, -pageRect.Y + rectInitial.Location.Y), rectInitial.Size);
            
            rectangles.Add(Rectangle.Ceiling(rect));

            location = Point.Empty;
            downLocation = Point.Empty;

            this.radPdfViewer1.Invalidate(); 
        }

        Point location = Point.Empty;
        Point downLocation = Point.Empty;
        Graphics g = null;
        
        private void PageElement_MouseMove(object sender, MouseEventArgs e)
        {
            if (Control.MouseButtons == System.Windows.Forms.MouseButtons.Left)
            {
                if (downLocation == Point.Empty)
                {
                    downLocation = e.Location;
                }
                location = e.Location;
                this.radPdfViewer1.Invalidate(); 
            }
        }
       
        private void PageElement_ElementPainted(object sender, PaintEventArgs e)
        { 
            RadFixedPageElement page = (sender as RadFixedPageElement);
            Rectangle rect = page.ControlBoundingRectangle; 
            SolidBrush semiTransBrush = new SolidBrush(Color.FromArgb(128, 255, 0, 0));

            if (location != Point.Empty && downLocation != Point.Empty)
            {
                e.Graphics.ResetTransform(); 
                Rectangle r = new Rectangle(downLocation, new Size(Math.Abs(location.X - downLocation.X),
                    Math.Abs(location.Y - downLocation.Y)));
                e.Graphics.FillRectangle(semiTransBrush, r);
            }
            
            foreach (Rectangle r in rectangles)
            {
                e.Graphics.ResetTransform();  
                e.Graphics.FillRectangle(semiTransBrush, new Rectangle(new Point(rect.X + r.Location.X, rect.Y + r.Location.Y), r.Size)); 
            }
        }

Note that implementing such custom functionality goes beyond the scope of the support service. Feel free to customize and extend the sample code in a way that meets your requirements best.

I hope this information helps.

 

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik